Dual mag failure

[aidanf]

For those of you who swear by your dual mags here is an excellent reminder of what can happen when you are flying behind a 40 year old single point of failure - great flying and recovery by the pilot BTW

 

https://forums.flyer.co.uk/viewtopic.php?f=13&t=104258

 

[N201MKTurbo]

Nobody here swears by their dual mag that I can recall. Quite a few of us have them and wish we didn't. 

We have talked a lot about properly securing the mag so it doesn't fall off.

[Mooney in Oz]

Improper maintenance is a major cause of issues such as application of the wrong type of gasket, incorrectly torqued nuts and reusing lock washers instead of new.  The search function will reveal all.

[Guest]

Magneto departure seems to still be a common issue despite an SB requiring new style clamps.  People still install wrong gaskets, wrong clamps, and reuse old hardware.  If installed correctly failure is rare.

Clarence

[Guest]

Here is the Lycoming SB covering correct installation of D 2/3000 series magnetos.

https://www.lycoming.com/sites/default/files/Dual Magneto Attachment.pdf

[jetdriven]

2 hours ago, M20Doc said:

Here is the Lycoming SB covering correct installation of D 2/3000 series magnetos.

https://www.lycoming.com/sites/default/files/Dual Magneto Attachment.pdf

...which is six years old now... 

[cliffy]

As mentioned, well known failure mode. I flew these on a Navajo through two engines, did all the mag work myself, always used new star washers any time the nut was loosened. Used proper torque. Never had a problem. Do the same today on my 2 mag engine. Any time the nut is loosened for any reason a new washer goes on, I buy them by the hundred pack! Just like spark plug washers. Cheap insurance. 

I have found mags with star washers totally flat from years of reuse.  

[carusoam]

We have found a Mooney pilot that is not on MS.

If he were to join us here. He would be familiar with this situation long before this situation occurred...

Go MS!

Thanks to @aidanf for sharing the link. That wasn't you Aidan, was it? Go ahead and add some detail to your avatar when you get a chance.

Best regards,

-a-

Edited June 6, 2017 by carusoam

[aidanf]

It was'nt me - thank goodness, as a fresh ppl I would probably not have been as smooth as this guy.

I am currently negotiating on a M20J -- so as soon as I have details I will update my avatar

[Bartman]

Shortly after my purchase of my J in 2007 I had an oil leak which turned out to be due to a loose Dual Mag. The pre purchase inspection was done at a fairly well known shop.....and they did the 500hr Mag inspection.  My local IA fixed it and he told me about using new fixtures.

About 2 years after that I had high EGTs in cruise and that was due to loss of one Mag in flight. The guy at KGCY said one of the internal gears, which IIRC he said was plastic had failed so we got a rebuilt Dual Mag and it was not cheap. It was during the time when there was a scare that the Dual Mag would no longer be supported or something like that. I remember hIm specifically telling me about the new style clamp, and that he set it at 25deg BTDC.  Sounds like he knew what he was doing with regard to the Dual Mag and that 25 was better than 20 for performance. 

[Alan Fox]

If you read the article , this is not a Mag failure , It is a maintenance failure.... 

[jetdriven]

1 hour ago, Bartman said:

Shortly after my purchase of my J in 2007 I had an oil leak which turned out to be due to a loose Dual Mag. The pre purchase inspection was done at a fairly well known shop.....and they did the 500hr Mag inspection.  My local IA fixed it and he told me about using new fixtures.

About 2 years after that I had high EGTs in cruise and that was due to loss of one Mag in flight. The guy at KGCY said one of the internal gears, which IIRC he said was plastic had failed so we got a rebuilt Dual Mag and it was not cheap. It was during the time when there was a scare that the Dual Mag would no longer be supported or something like that. I remember hIm specifically telling me about the new style clamp, and that he set it at 25deg BTDC.  Sounds like he knew what he was doing with regard to the Dual Mag and that 25 was better than 20 for performance. 

25° is the only legal setting for the dual magneto.  It's optional on the other models.  A poor choice, but an option. 

[mooneyflyfast]

I swear by my dual mag because I have a mechanic who knows how to install it so it doesnt fall off. I follow the recommended inspection schedule of 500 hours and I check the nuts that hold it on when I have the cowling off. In 2,200 hours over 19 years I have never had a mag problem. This guys point of failure was his mechanic. It had nothing to do with the mag being a 40 year old design.. Guess I am a little thin skinned about this but I dont like to see the blame misplaced on the mag when the problem was failure to follow basic maintenance procedures. 

[Piloto]

On ‎6‎/‎6‎/‎2017 at 8:51 AM, Alan Fox said:

If you read the article , this is not a Mag failure , It is a maintenance failure.... 

+1 At every oil check I always check the magneto mounting nuts.

José

[Carl S]

We went over this subject a bit at the MAPA PPP in Chattanooga last weekend. It was an interesting part of the course and checking the mounting nuts is something I am adding to my list of things to do at oil changes. I am considering locknuts also. 

It is my understanding that all rebuilds done by Lycoming will be converted to the dual mag case.